By longstanding tradition, a minimally valid QSO requires the exchange of callsigns, a signal report or some other information, and acknowledgments. WSJT-X is designed to facilitate making such minimal QSOs using short, structured messages. The process works best if you use these formats and follow standard operating practices. The recommended basic QSO goes something like this:

Standard messages consist of two callsigns (or CQ, QRZ, or DE and one callsign) followed by the transmitting station’s grid locator, a signal report, R plus a signal report, or the final acknowledgements RRR or 73. These messages are compressed and encoded in a highly efficient and reliable way. In uncompressed form (as displayed on-screen) they may contain as many as 22 characters.

Signal reports are specified as signal-to-noise ratio (S/N) in dB, using a standard reference noise bandwidth of 2500 Hz. Thus, in the example message above, K1ABC is telling G0XYZ that his signal is 19 dB below the noise power in bandwidth 2500 Hz. In the message at 0004, G0XYZ acknowledges receipt of that report and responds with a –22 dB signal report. JT65 reports are constrained to lie in the range –30 to –1 dB, and values are significantly compressed above about -10 dB. JT9 supports the extended range –50 to +49 dB and assigns more reliable numbers to relatively strong signals.

Users often add some friendly chit-chat at the end of a QSO. Free-format messages such as “TNX ROBERT 73” or “5W VERT 73 GL” are supported, up to a maximum of 13 characters, including spaces. In general you should avoid the character / in free-text messages, as the program may then try to interpret your construction as part of a compound callsign. It should be obvious that the JT4, JT9, and JT65 protocols are not designed or well suited for extensive conversations or rag-chewing.

The slow modes JT4, JT9, JT65, and QRA64 allow nearly 10 seconds at the end of each one-minute receiving sequence — enough time for you to inspect decoded messages and decide how to reply. The 15-second T/R cycles of FT8 allow only about two seconds for this task, which is often not enough. For this reason a basic auto-sequencing feature is offered. Check Auto Seq on the main window to enable this feature:

When calling CQ you may also choose to check the box Call 1st. WSJT-X will then respond automatically to the first decoded responder to your CQ.

A special NA VHF Contest mode can be activated for FT8 and MSK144 modes by checking a box on the main window. This mode is configured especially for contests in which four-character grid locators are the required exchange. When NA VHF Contest mode is active, the standard QSO sequence looks like this:

In contest circumstances K1ABC might choose to call CQ again rather than sending 73 for his third transmission.

Do not use VHF Contest Mode on an HF band or in conditions where worldwide propagation is available. See Protocol Specifications for further details.

Compound callsigns such as xx/K1ABC or K1ABC/x are handled in one of two possible ways:

A list of about 350 of the most common prefixes and suffixes can be displayed from the Help menu. A single compound callsign involving one item from this list can be used in place of the standard third word of a message (normally a locator, signal report, RRR, or 73). The following examples are all acceptable messages containing Type 1compound callsigns:

The following messages are not valid, because a third word is not permitted in any message containing a Type 1compound callsign:

A QSO between two stations using Type 1 compound-callsign messages might look like this:

Notice that the full compound callsign is sent and received in the first two transmissions. After that, the operators omit the add-on prefix or suffix and use the standard structured messages.

Prefixes and suffixes not found in the displayable short list are handled by using Type 2 compound callsigns. In this case the compound callsign must be the second word in a two- or three-word message, and the first word must be CQ, DE, or QRZ. Prefixes can be 1 to 4 characters, suffixes 1 to 3 characters. A third word conveying a locator, report, RRR, or 73 is permitted. The following are valid messages containing Type 2 compound callsigns:

In each case, the compound callsign is treated as Type 2 because the add-on prefix or suffix is not one of those in the fixed list. Note that a second callsign is never permissible in these messages.

QSOs involving Type 2 compound callsigns might look like either of the following sequences:

Operators with a compound callsign use its full form when calling CQ and possibly also in a 73 transmission, as may be required by licensing authorities. Other transmissions during a QSO may use the standard structured messages without callsign prefix or suffix.

Before attempting your first QSO with one of the WSJT modes, be sure to go through the Basic Operating Tutorialabove as well as the following checklist: